Even if Switch 2 comes out 2023, it doesn't "replace" the Switch anyway. You're probably talking a $350 product at launch and the people buying the Switch 2 for the first 1-2 years will be people overwhelmingly who owned a Switch for 4+ years by that time and are looking for a sexier, newer console.
The money Nintendo would be taking away with a Switch 2 would likely be PS5/XBSX potential sales, not original Switch systems. There is lots of overlap with PS4/XB1/Switch owners, so really more than likely the type of person who's buying a Switch 2 in 2023 is the type of person who would be looking at an PS5 or XBSX ... not buying like some 3rd redesign of a system they already have.
The people who buy a system in year 6/7/8 are not the consumer that buys a brand new console no matter what, often times you're talking about parents looking to buy a first game system for a very young child or someone who doesn't care when games come out and wants an absolutely over-ripened software library with possibly discounted games and/or extreme budget conscious consumer that refuse to spend over $200 or something like that for a game machine.
Switch 2 doesn't replace the Switch not until Switch 2 Lite (a cheaper, more portable version) would be available and you're probably talking 2025 or 2026 for that. A $350 Switch 2 and a $169.99 Switch Lite are not competing for the same consumer at all.
Software wise both can be supported for a long, long time, Nintendo supported the 3DS for well over a year after the Switch's release with a new release averaging out about every month through 2017 and into 2018 and still were releasing new product into 2019.
Besides by the time you reach like 1000+ games, lol, there's more than enough software product there anyway. The difference nowadays is there are digital stores that can keep a back catalog of thousands of games up basically indefinitely. Back in the day the reason systems got phased out is because retail stores had to make space/room for younger, better selling systems, you couldn't keep stocking Super NES games when Playstation, N64 needed that space. But today? There's no reason honestly to even stop selling the 3DS. Stores can stock the system itself easily and people can buy it and simply purchase games off the eShop.
If Nintendo really wanted to and they were willing to say make all DS/3DS eShop titles $19.99-$29.99 flat ... they could sell the 3DS for another 4-5 years probably.
